ASSOCIATION OF miRNA EXPRESSION PATTERN WITH OUTCOME OF LETROZOLE THERAPY IN BREAST CANCER PATIENTS.

Unlabelled: Breast cancer (BC) remains the most prevalent tumor and the leading cause of death among women worldwide, despite the advancements in diagnosis and new treatments. A significant challenge in BC treatment is the acquired or de novo resistance of tumors to systemic therapy. To overcome this obstacle, personalized treatment is needed, with a focus on finding biomarkers capable of predicting the response to therapy. MicroRNAs (miRNAs) have emerged as potential markers due to their diverse clinical applications.

Aim: To examine the potential prognostic significance of miR-125b-2, -155, -221, and -320a expression in the tumor cells of individuals with hormone-dependent BC before undergoing neoadjuvant hormonal therapy.

Materials And Methods: The study is based on a retrospective analysis of the treatment outcome of 56 patients with stage II-III locally disseminated hormone-dependent BC. The real-time quantitative reverse transcription polymerase chain reaction was performed on the biopsy material to assess the expression of miR-125b-2, -155, and -221 before neoadjuvant hormonal therapy with aromatase inhibi- tor letrozole to predict clinical response.

Results: Most HER2/neu+ BC patients had low levels of miR-155 and miR-221 expression in tumor biopsy specimens. Tumors that responded well to letrozole exhibited lower levels of miR-125b-2 and miR-221 compared to non-responsive tumors.

Conclusions: miR-125b-2, -155, and -221 expres- sion can predict resistance to the letrozole treatment of BC.